Cured polymer compositions and their preparation



' as practicable,

, atures of the order of about nited States Patent Ofiice amass3,278,499 CURED PULYMER COMPQSITIUNS AND THEIR PREPARATION Thomas H.Shepherd, Hopewell, N..I., assignor, by mesne assignments, to Mobil OilCorporation, a corporation of New York No Drawing. Filed Sept. 23, 1963,Ser. No. 310,875

20 Claims. (Cl. 26079.5)

Thi invention relates to a method for curing (i.e.', crosslinking)normally solid polymers and copolymers of More particularly, thiinvention relates to a novel method for curing normally solidpolypropylene and the cured product thereof.

In accordance with this invention, a normally solid poly- 1'0 .a-olefinsand to the cured products obtained thereby.

mer or copolymer of an alpha-olefin is cured by heating,

at an elevated temperature, a composition comprising the polymer to becured in mixture with a small amount, based on the weight of thepolymer, of sulfur and a dihalosulfonamide as the curing agent. In morespecific embodiment, the invention is carried out by heating a mixturecomprising 100 parts by weight'of a polymer or copolymer to be cured,from about 1 to about parts by weight of a dihalosulfonamide andsulfurin an amount up to about one half the weight of the curing agent.

Still more specifically, and although the amount of the 1 generallybeing less than half the weight of that of the curing agent and,generally, from about 0.5 to about 1 part by weight per 100* copolymer.

In a particular embodiment of the present invention, the

parts by Weight of the polymer or polymer or copolymer to be cured isground and slurried with the curing agent and sulfur in an organicliquid, suitable examples of which include acetone, diethyl ether, andothers, with the compounding being accomplished by evaporating thesolvent. Thereafter the composite is dried at about 200-250 then becured by heating at an elevated temperature, as for example, from about275 to about 425 F., and more specifically, from about 325 to about 375F. for a length of time sufiicient to allow adequate cu ring, usuallyfor at least about 3 minutes and, generally, from about 5 to about 60minutes.

The above described method is suitable for a small-scale application ofthe method of the present invention. The present method, however, may beapplied similarly in a larger scale.

such as a Banbury, Koneader or screw extruders, particularly the twinscrew extruder, and the like. In all cases the final temperature of thebatch should be as low ing point of the polymer. Although maximumtemper- 425-450" F. are encountered in the mixing cycle, preferably themixer employed discharges the cor'npound' at a temperature considerablylower. Significantly, many of the above internal mixers are particularlyeffective'in dispersing the compounding ingredients. Consequently, insuch a process, the mixing time would be frequently shortened to about3-5 minutes and would rarely exceed 5--10 minutes.

The present invention is especially applicable to the curing ofpolypropylene and, hence, theinvention is de- 4 parts by weight agentper 100 parts by weight of the polymer F. The polymeric composition can.

In such an application the compounding is achieved on conventionalroller mills or in internal mixers preferably exceeding only slightlythe melt- Patented Get. 11, 1966 scribed herein with particular emphasison polypropylene. However, it is also applicable to the curing of otherpolymers or copolymers of alpha-olefins, for example, poly- 'mers orcopolymers obtained from one, two or more of the following olcfins:ethylene, propylene, l-butene, 1- pentene, 4-methyl-l-pentene,S-methyl-l-hexene, 4-ethyl- 1-pentene, and, in general, otheralpha-olefins containing up to carbon atoms. In referenceto copolymers,it is preferred that one of the olefins. from which the copolyfmerisobtained be ethylene or'propylene. Additionally, the invention isapplicable to the curing of a broadfspectrum of copolymer compositionsincluding terpolymers and higher combinations. In commercial practicewith polymers of particularly ben'eficial utility, the copolymers mostfrequently comprise ethylene, propylene, l-butene or combinationsthereof. With more difiiculty, the invention is also applicable to thecuring of a copolymer of one of the above-mentioned alpha-olefins andanother olefin having a double bond which is not in the alpha position.Examples of such other olefins include the followingi 2- 4 butene,Z-pentene, Z-hexene, 3-hexene, and others.-

-The dihalosulfonamides useful for practice of the present inventionhave the following formula:

ing to the following wherein X 1 and X 2 are halogen atoms, examples ofwhich include chlorine or bromine, and preferably chlorine; and whereinR is a cyclic hydrocarbon group, such as phenyl, naphthyl, cyclohexyl,etc., and preferably phenyl, and which hydrocarbon group may havesubstituted thereon one or more alkyl groups such as methyl, ethyl,propyl,

' fonamide, N,N-dichlorocumenesulfonamide, and others.

By the method of the present invention, polymers or copolymers ofalpha-olefins can be cured to give products having a high tensilestrength, e.g., from about 4000- 5000 psi. at yield, an elongation atbreak of about 10- 500% or more, while exhibiting excellent chemicalinertness.

The following examples set forth embodiments of the invention forpurposes of illustration and not limitation.

Exariiple A In this example polypropylene,N,N-dichl0robenzenesulfonarnide (DCB) and sulfur were combinedaccordformulas (all parts by weight) Formula A B i C Polypropylene 100100 D C B 2 2 4 Sulfur 1 0. 5 0. 5

Slabs of the composition of Formula A were cured at 345 F. for varyingperiods of time. The physical properties of the various products wereevaluated and the results are given below:

Curing time, minutes..- 5 Tensile strength, s i.:

Break Tensile modulus, p.s.i Elongation, pcreent Gel, percent Example BSlabs of the composition of Formula B were cured at 335 F. for varyingperiods of time. The physical properties of the various products wereevaluated and the results are given below:

Curing time, minutes. 5 Tensile strength, p.s.1.:

Yield 5, 080

Brea Tensile modulus, Elongation, percent Gel, percent Example C Slabsof the composition of Formula C were cured at 335 F. for varying periodsof time. The physical properties of the various products were evaluatedand the results are given below:

Curing time, minutes 5 Tensile strength, p.s.i.:

Elongation, percent... Gel, percent The above results clearly illustratethat a polymer of an alpha olefin, exemplified by propylene, compoundedwith a dihalosulfonamide and sulfur can be eflectively cured to give across-linked product which exhibits superior strength, ductility andchemical inertness.

Although the present invention has been described with preferredembodiments, it is to be understood that modifications and variationsmay be resorted to, without departing from the spirit and scope of thisinvention, as those skilled in the art will readily understand. Suchvariations and modifications are considered to be within the purview andscope of the appended claims.

What is claimed is:

1. A method for curing normally solid polymers of an alpha-olefin whichcomprises heating a normally solid polymer of an alpha-olefin, blendedwith a small amount based on the weight of said polymer, of adihalosulfonamide as a curing agent, and sulfur in an amount by weightless than that of said curing agent, at a temperature above the meltingpoint of said blend, for a period of time sufficient to cross-link saidpolymer.

2. A method as defined in claim 1 in which the blend by weight containsfrom about 0.01 to about 0.05 part of the dihalosulfonamide, per part ofthe polymer, and sulfur in an amount up to about /2 the weight of thedihalosulfonamide.

3. A method as defined in claim 1 wherein the blend is heated at atemperature of from about 275 F. to about 425 F. for at least 3 minutes.

4. A method as defined in claim 1 wherein the blend by weight containsfrom about 0.01 to about 0.05 part of the di-halosulfonamide, per partof the polymer and sulfur in an amount up to about /2 the weight of thedihalosulfonamide, and wherein the blend is heated at a temperature offrom about 275 F. to about 425 F. for at least 3 minutes.

5. A method as defined in claim 1 wherein the normally solid polymer ispolypropylene.

6. A method as defined in claim 1 wherein the normally solid polymer isa copolymer of two or more different alpha-olefins.

7. A method as defined in claim 1 wherein the normally solid polymer isa copolymer of an alpha-olefin and an olefin unsaturated other than inthe alpha position.

8. A method as defined in claim 1 wherein the dihalosulfonamide has thefollowing structure:

in which X and X are halogen atoms and R is a hydrocarbon radical.

9. A method as defined in claim 8 whereon X are chlorine atoms.

10. A method as defined in claim 8 wherein R is an aromatic hydrocarbonradical.

11. A method as defined in claim 1 wherein the dihalosulfonamide curingagent is N,N-dichlorobenzenesulfonamide.

12. A composition, useful in the preparation of cured polymers ofalpha-olefins, comprising a normally solid polymer of an alpha-olefin,blended with a small amount, based on the weight of said polymer, of adihalosulfonamide as a curing agent, and sulfur in an amount by weightless than that of said curing agent.

13. A composition, useful in the preparation of cured polymers ofalpha-olefins, comprising a blend as defined in claim 12 which containsby weight from about 0.01 to about 0.05 part of said dihalosulfonamideper part of said polymer, and sulfur in an amount up to about /2 theweight of said dihalosulfonamide.

14. A composition, useful in the preparation of cured polymers ofalpha-olefins, comprising a blend as defined in claim 12 wherein thenormally solid polymer is polypropylene.

15. A composition, useful in the preparation of cured polymers ofalpha-olefins, comprising a blend as defined in claim 12 wherein thenormally solid polymer is a copolymer of two or more differentalpha-olefins.

16. A composition, useful in the preparation of cured polymers ofalpha-olefins, comprising a blend as defined in claim 12 wherein thenormally solid polymer is a copolymer of an alpha-olefin and an olefinunsaturated other than in the alpha position.

17. A composition, useful in the preparation of cured polymers ofalpha-olefins, comprising a blend as defined in claim 12 wherein thedihalosulfonamide has the following structure:

and X in which X and X? are halogen atoms and R is a hydroc rb n rdical.

References Gated by the Examiner UNITED STATES PATENTS Bowman et al.26079.5 McFarland 26079.5 Robinson et al 260-795 Reynolds et al. 260-949JOSEPH L. SCHOFER, Primary Examiner. 10 L. EDELMAN, Assistant Examiner.

1. A METHOD FOR CURING NORMALLY SOLID POLYMERS OF AN ALPHA-OLEFIN WHICHCOMPRISES HEATING A NORMALLY SOLID POLYMER OF AN ALPHA-OLEFIN, BLENDEDWITH A SMALL AMOUNT BASED ON THE WEIGHT OF SAID POLYMER, OF ADIHALOSULFONAMIDE AS A CURING AGENT, AND SULFUR IN AN AMOUNT BY WEIGHTLESS THAN THAT OF SAID CURING AGENT, AT A TEMPERATURE ABOVE THE MELTINGPOINT OF SAID BLEND, FOR A PERIOD OF TIME SUFFICIENT TO CROSS-LINK SAIDPOLYMER.
 8. A METHOD AS DEFINED IN CLAIM 1 WHEREIN THE DIHALOSULFONAMIDEHAS THE FOLLOWING STRUCTURE: